1. Field of the Invention
The present invention relates to a magnetic head structure including a monitor element to be used in polishing for forming a medium-facing surface of a head element portion and a method for manufacturing the magnetic head structure.
2. Description of the Related Art
In general, when a magnetic head is produced, head element portions (head element structures) prepared by laminating at least a playback element and a recording element are formed and arrayed into a plurality of rows on a wafer (substrate). Thereafter, the wafer is cut into each row, and a medium-facing surface is formed (an element height is regulated) by polishing, so that a bar-shaped magnetic head substrate in which a plurality of head element portions are disposed in a single line on a wafer or individual (chip-shaped) magnetic heads, in which one head element portion is formed on a wafer, are produced. In the present specification, the bar-shaped magnetic head substrate and the chip-shaped magnetic head are collectively referred to as a magnetic head structure.
Heretofore, in polishing for forming the above-described medium-facing surface, a wafer end surface is polished in a element height direction while the element resistance is detected by passing a current through a playback element or a playback-side monitor element formed simultaneously with the playback element, and the polishing is terminated when the element resistance reaches a predetermined value. However, when the element height is regulated on the basis of the resistance value of the playback element or the playback-side monitor element, it is difficult to grasp an actual element height dimension of a recording element. Since the element height dimension of the recording element is an important factor that contributes to recording characteristics, the element height dimension must be regulated precisely. Consequently, in recent years, it has been proposed that a playback-side monitor element having a resistance value which is changed in accordance with the element height dimension of the playback element is formed simultaneously with the playback element and, in addition, a recording-side monitor element having a resistance value which is changed in accordance with the element height dimension of the recording element is formed simultaneously with the recording element. Each of the playback element and the recording element is polished to a position suitable for obtaining desired characteristics while a current is passed through the playback-side monitor element and the recording-side monitor element so as to detect their respective element resistances.
As shown in, for example, FIG. 7, the recording-side monitor element can be composed of a resistance film 131 formed simultaneously with the recording element, a lead conductor 132 located as a layer below the resistance film 131, and a contact conductor 133 for conductively connecting the resistance film 131 and the lead conductor 132. The peripheries of the resistance film 131, the lead conductor 132, and the contact conductor 133 are covered with insulating material films 140, 141, and 142 formed from, for example, Al2O3.
Thin film magnetic heads including a monitor element to be used for controlling polishing are described in, for example, Japanese Unexamined Patent Application Publication No. 2005-339781, Japanese Unexamined Patent Application Publication No. 2006-48806, and Japanese Unexamined Patent Application Publication No. 2006-73088.
In recent years, in order to achieve higher recording density, many recording elements of perpendicular recording system have been used, which includes a main magnetic pole layer for applying a perpendicular recording magnetic field to a recording medium, an auxiliary magnetic pole layer for receiving a recording magnetic field returned after passing the recording medium, a recording coil for applying a recording magnetic field to the main magnetic pole layer, and the like. The element height dimension in this perpendicular recording element is a height direction dimension of a pole straight portion of the main magnetic pole layer, a so-called neck height. In order to regulate the neck height with high precision, it is preferable that a resistance film of the recording-side monitor element is formed simultaneously on the same plane as that for the main magnetic pole layer, from the same material as the material for the main magnetic pole layer. However, since the main magnetic pole layer is formed having a large thickness in general, when the recording-side monitor element formed simultaneously with the main magnetic pole layer is used, the monitor resistance before polishing is small, and the amount of change in resistance due to polishing is decreased. Therefore, there is a problem in that a polishing termination position is hard to be detected.
For a means for solving this, recently, it is known that a resistance film of a recording-side monitor element is formed by using a main magnetic pole plated base layer disposed directly below the main magnetic pole layer, as described in Japanese Unexamined Patent Application Publication No. 2006-73088, for example.
The recording-side monitor element by using the main magnetic pole plated base layer can be disposed by forming a resistance film on a contact conductor simultaneously with the main magnetic pole layer plated base layer, forming a mask covering a monitor region to be formed on this resistance film, removing the resistance film exposed at the mask by milling, and furthermore, removing the mask by wet etching. Since the main magnetic pole layer plated base layer has a very small thickness as compared with the thickness of the main magnetic pole layer, satisfactory monitor sensitivity can be obtained.
However, as shown in FIG. 7, a known recording-side monitor element has a structure in which the contact conductor 133 is extended outward as compared with the resistance film 131. Therefore, when the above-described mask is removed by wet etching, the extended portion β of the contact conductor 133 is also etched simultaneously. Consequently, not only the element resistance of the resulting recording-side monitor element (contact conductor) is changed, but also the contact conductor and the lead conductor are broken by etching so as to bring the resistance film out of conduction at worst, and the function as the recording-side monitor element is not exerted.
In the configuration of the known recording-side monitor element, the resistance film and the contact conductor is cut together by polishing. Therefore, a change in resistance of the resistance film and a change in resistance of the contact conductor appear as changes in element resistance of the recording-side monitor element. In order to regulate the neck height of the main magnetic pole layer, it is preferable that the polishing termination timing is controlled merely by the change in resistance of the resistance film formed simultaneously with the main magnetic pole plated base layer.